On our way through Montana we decide to stay at the Horse Creek Campground, located at the Clark Creek Reservoir, 20-some miles south of Dillon, MT.
This is one of several free campgrounds around the reservoir. Amenities inclide pit toilets, many trash bins, a boat ramp, covered shelters, fire rings, and more or less level places to park on the gravel. When all sites are taken there is a large grass area to put your rig. We had excellent Verizon cell and data service here. Over all a very nicely maintained free campground with great views and the city of Dillon nearby to resupply.